The Smith Optics Threshold is a perfect update to the very successful Mainline. Extremely lightweight and includes an adjustable temple. The Patented interchangeable lens system creates a sleek and subtle design allowing easily interchangeable lenses perfect for the running trail, golf course, or weekend ride. Smith utilizes distortion-free, 9 base lenses to provide precise optical clarity and maximize coverage while minimizing peripheral exposure to sun, wind, and glare. 16 replacement lens tints to choose from.